Mike Caldwell’s Casascius coins were the first physical bitcoin anyone could hold — brass and silver rounds with private keys hidden under tamper-proof stickers. Minted from September 2011 until November 2013, when the U.S. FinCEN told Caldwell he needed a money-transmitter license to continue, they became the most iconic artifacts in Bitcoin history. But they had a problem: buyers had to trust that Caldwell had destroyed the keys after sealing the coins. That trust gap has haunted the idea of physical bitcoin ever since.
The Casascius trust
Caldwell generated each key on an airgapped machine, printed it, glued it to the coin, and destroyed the copy on his computer. The honeycomb-pattern stickers showed clear marks if removed, so third-party buyers could check. His reputation remains strong — he never cheated. But the system relied entirely on one person not cheating. That’s not a scalable model.
RavenBit’s attempt
RavenBit launched a year after Casascius shut down, trying to decentralize the minting problem. Users generated their own keypair on a blank coin, pasted it, and applied a tamper-proof sticker themselves. The project has since been abandoned. The lesson: asking users to generate keys and apply stickers is clunky, and the industry realized a higher-tech solution was needed.
Opendime’s hardware answer
Coinkite’s Opendime is a different beast. It’s a small computer chip purpose-built to be a Bitcoin bearer asset. The chip generates its own private-public key pair, so no mint — and no trusted third party — is involved. You can pass the device like cash, and the recipient knows the key was never exposed. NVK, co-founder of CoinKite, put it bluntly: “Bitcoin is digital money. All we can do is an analog backup. Maybe someone cracks doing secp256k1 by hand in the future.”
For now, Opendime is the closest the industry has to a trustless physical bitcoin. Whether it catches on is an open question — but it solves a problem that’s been kicking around since 2011.
